The BS9K set was designed to modify the color scheme of the default stylesheet in order to signal general differences in the way that individual reddits function. Apart from some simplification of the "submit a link" and "create our own community" buttons, only color elements have been changed. Below is a legend of the intended functional meaning of each theme in the set.

Theme

Reddits with this theme...

Example

Code

Ahi

... are used by the moderators of related reddits to carry out tasks related to moderation. As an example, some moderators use a separate reddit as a public log of removed comments, in order to ensure a measure of transparency and accountability. Others use moderation reddits in order to keep up with mod discussions, which is sometimes easier than carrying on involved conversations in mod mail.

... are meta or service reddits. In this context, "meta" means any reddit specifically about this site or its users, and "service" means any reddit dedicated to providing a service that helps redditors get more use out of Reddit.

... depend on a local etiquette or ruleset in order to highlight types of content that might otherwise get lost in the queue of other reddits. For these reddits to work as intended, it is doubly important that users approach conscientiously submissions and comments conscientiously.

FAQ

Why did you create this set?

There are thousands of communities on Reddit, and many of them are attempting to adapt the basic functionality of the site to tasks not really encompassed by the original design. Those reddits sometimes depend on a different set of expectations in order to work. The idea behind the BS9k set was to color-code several popular functions so that users could discern at a glance what expectations bear on a reddit they're visiting for the first time. At first, of course, most users won't know what the different themes mean, but my hope is that, if Reddit mods implement these themes properly and widely, we can build up those associations and educate the community as to the implicit meaning of different colored themes.

Can I use one of the themes in this set?

Yes; in fact, I encourage you to do so. If you moderate a reddit, then you're part of the crowd this set was designed for.

I've got my own custom CSS; why should I use a style from this set?

Maybe you shouldn't. If you're happy with the CSS you've got, by all means, stick with it. This set is strictly for moderators who want to help try and build a culture of associations by color-coding their reddits according to basic intended functionality. I don't expect the set to ever be anything more than a voluntary endeavor.

How?

In the moderation box of the reddit you moderate, click Community settings, then edit the stylesheet, and paste the code for the theme you want to use into the text box there. The new style will take effect when you click the save button.

Should I credit you?

It would be nice if you did. There's already a credit in the code of each theme, so as long as you don't manually remove that, anyone who views the style sheet will likely see that. If you want to go a step beyond that, paste the following signature somewhere in your sidebar:

Doing so not only credits me, but it also links back to this post, so that people can read about each of the themes and what they're meant to indicate about the reddits that use them.

Can I modify one of these themes?

Sure; I'm not the boss of you.

My reddit fits more than one category. Which should I use?

The table near the top of this post is ordered according to what I think should be the priority of categories, with the higher priority categories higher on the list. For example, if you run a service reddit that is also text-only, I would suggest that you use the Grass theme, rather than the Latte theme, simply because that information will generally be more important to the reader.

I like one of the themes, but my reddit doesn't really serve the function that theme is meant to indicate. Can I still use it?

I wouldn't advise it, since, if this set catches on, mismatching themes might lead people to misuse your reddit. But ultimately, the decision is up to you. If you decide to mismatch one of these themes anyway, you can cut down on confusion by modifying that theme, especially if you have an image-based banner to put in the header.

I'm not really interested in using any of these themes, but I do want to customize the style of my reddit. Will you code something for me?

No. I spend too much time tweaking Reddit as is. Besides, editing the style sheet isn't terribly difficult. You can probably do it yourself. Check out the W3C's CSS page for the basics, and drop in at /r/RedditHax if you need some additional help.

I don't see what's changed....I still see w3schools.com linked? While it's your post and you can put what you want, the criticism from the community is that W3Schools has too much inaccurate information and shouldn't be referenced or trusted...

W3C is a non-profit standards body.

W3Schools is a for-profit website that has nothing at all to do with the W3C.

I know that the idea of "tiering" out subreddits sounds a bit sketchy and rigid, but I'm not necessarily discriminating against content. It would simply be easier to discern the level of effort required in each subreddit. The majority of subreddits would fall under the standard reddiquite and not need any sort of distinction. Subreddits that set and enforce posting rules could adopt the high tier theme to distinguish them, where as NSFW subreddits could adopt another theme (sort of like how 4chan distinguishes between SFW and NSFW boards with a different background.

By the way, the themes look awesome either way, I adopted one for /r/computers. Good work!

I know that the idea of "tiering" out subreddits sounds a bit sketchy and rigid

I'm sure some people would appreciate it. That just wasn't what I was interested in parsing out here. But I've done a lot of the prep work for anyone who wants to set up another color-coded set. Just take the tags that I pulled from the default style sheet and change the colors I've assigned to them. Oh, and remove the .titlebox tags, since those are strictly for the sidebar signature.

Incidentally, are there any general categories I'm missing in the current set? I'm looking for something to assign to "Latte." If I can't think of another category, I'll probably just split off Manilla into two distinct categories, one for individuals, and another for groups.

Then it clearly wouldn't fall under the "user-generated content" clause of that theme. The question, then, is whether or not it applies under the "emphasizes discussion" clause. And that's really up to the mods. If they want their sub to be primarily about discussion, then adopting that theme would be one way of signalling that emphasis. In general, I'd look at it this way: if you're not specializing in user-generated content, and you're still wondering whether or not the Latte theme is right for your sub, ask yourself, "Would I be willing to make my sub text-only?" If not, then you're probably better off sticking with the standard blue theme.

Also, any chance you could put some comments in the css indicating what affects the sidebar? I'm testing out latte right now and it killed the formatting on my sidebar. I'm not much of a css wizard, but I've looked through it and I can't figure out what is overriding the old css. I put the latte css on top, with the old css below it. My fault. I loaded a cached version of the stylesheet.

I'll take a look at it. In the meantime, you're free to modify it on your own reddits. If you want an easy way to do it without changing the color scheme, just add text-decoration: underline to the a tag. That should do it.

Sure. I'm still working out the functional meanings of each, but the idea is that anyone who moderates a sub could use these themes. They're most useful if everyone uses them according to the functional meanings assigned to each, since that helps build recognition of those meanings, but ultimately use is voluntary, as is using them according to their intent.

The stylesheet from each appends the name of the theme to the link when you add it. That's where the word is coming from. If you don't want it adding that word, there's a tag you can remove from the code...